Gene Expression and Signal Transduction in Transformatio

我们研究的主要目的是了解分化、细胞生长和肿瘤转化的分子和遗传机制。我们研究了小鼠和人类实验肿瘤系统中的癌基因、肿瘤抑制基因和信号转导蛋白，包括BALB/c小鼠浆细胞瘤、b细胞淋巴瘤和NIH 3T3细胞等。这些是有价值的实验模型，因为它们可以用于设计更具体的治疗和预防措施，用于人类多发性骨髓瘤、非霍奇金淋巴瘤和其他人类恶性肿瘤。与人类伯基特淋巴瘤一样，BALB/c浆细胞瘤的特征是原癌基因c- myc的组成性表达。为了确定完全转化需要哪些额外的遗传改变，我们正在使用微阵列杂交研究全局基因表达，以跟踪从恶性前期到完全恶性浆细胞肿瘤进展过程中的基因表达变化。我们还利用微阵列杂交研究来探索小鼠浆细胞肿瘤发展的病理生理机制，以及某些转基因和病毒致癌基因加速这一肿瘤过程的机制。在分化和肿瘤转化的信号转导研究中，我们正在研究丝氨酸/苏氨酸激酶蛋白激酶C （PKC）家族的异构体特异性特征。我们一直在关注δ和ε同工酶，它们对细胞增殖有相反的作用。我们已经证明，大多数同工酶特异性决定因子位于这些PKCs的催化一半（羧基末端结构域），通过创建互惠嵌合cdna编码一半PKC-delta和一半PKC-epsilon的分子。我们正在进一步剖析催化结构域的结构，以确定哪些子结构域决定PKC异构体特异性功能，重点关注羧基末端50个氨基酸，即“V5结构域”。我们也在研究PKC参与细胞凋亡、细胞骨架相关的细胞形状和运动变化的本质，并与c-myc原癌基因合作。我们已经证明，磷酸化酯激活过表达的pkc - δ会破坏人和小鼠淋巴细胞中的肌动蛋白细胞骨架，导致细胞膜褶皱（细胞运动所需的表面改变）的丧失，以及这些细胞典型的细长形状的丧失。我们已经证明，这种效应是由于pkc介导的接头分子paxillin中关键酪氨酸残基磷酸化的变化。

The chief objective of our research is to understand the molecular and genetic mechanisms responsible for differentiation, cell growth, and neoplastic transformation. We study the oncogenes, tumor-suppressor genes and signal-transducing proteins in mouse and human experimental tumor systems, including BALB/c mouse plasmacytomas, B-cell lymphomas, and NIH 3T3 cells, among others. These are valuable experimental models, because they can be used to devise more specific therapy and preventive measures for human multiple myeloma, non-Hodgkin's lymphomas, and other human malignancies. BALB/c plasmacytomas, like human Burkitt lymphomas, are characterized by constitutive expression of the proto-oncogene, c-Myc. To determine which additional genetic alterations are required for complete transformation, we are using microarray hybridization studies of global gene expression to follow changes in gene expression during progression from pre-malignant to fully malignant plasma cell tumors. We are also using microarray hybridization studies to probe the pathophysiological mechanisms at work in development of plasma cell tumors in mice and the mechanisms whereby certain transgenes and viral oncogenes accelerate this neoplastic process.In the study of signal transduction in differentiation and neoplastic transformation, we are investigating the isoform-specific features of the protein kinase C (PKC) family of serine/threonine kinases. We have been focusing on the delta and epsilon isoenzymes, which have opposing effects on cell proliferation. We have shown that most of the isoenzyme-specific determinants are located in the catalytic half (the carboxyl-terminal domain) of these PKCs by creating reciprocal chimeric cDNAs that encode molecules that are half PKC-delta and half PKC-epsilon. We are further dissecting the structure of the catalytic domain to determine which sub-domains determine PKC isoform- specific functions, focusing on the carboxy-terminal 50 amino acids, the "V5 domain." We are also studying the nature of PKC's involvement in apoptosis, in cytoskeleton-related changes in cell shape and motility, and in cooperation with the c-myc proto-oncogene. We have shown that phorbol ester-activation of overexpressed PKC-delta disrupts the actin cytoskeleton in human and mouse lymphocytes, leading to the loss of membrane ruffling, a surface alteration needed for cell movement, and the loss of the typical elongated shape of these cells. We have demonstrated that this effect is due to PKC-mediated changes in phosphorylation of key tyrosine residues in the adaptor molecule, paxillin.